Valve is suing Activision after alleging that the publisher has deliberately underpaid a $2.39 million royalty sum recently awarded to the Half-Life series developer.

The new clash has arisen from the infamous 2002 dispute between Valve and Sierra, where both parties at the time fought on allegations that Sierra had unfairly licensed Valve games to cyber-cafes. That dispute was put on hold in 2005 when both parties agreed that an audit arbitrator would determine if and what was owed to Valve.

On April 6, some four years later, the arbitrator concluded that Valve was owed a total sum of $2,391,932. That figure landed at Activision’s doorstep as Sierra was absorbed in the 2008 Activision Blizzard merger.

Later in April, Activision signed a cheque to Valve for $1,967,796 – some $424,000 less than the audit arbitrator’s decision.

Activision alleges that it left out $424,000 in final payment because that was the precise sum it had overpaid Valve in previous years.

According to court documents sought by Game Politics, Activision has refused to pay anything beyond the $1.9m, and has already threatened to sue Valve to recover the $424,136 if Valve persists in seeking the $2,391,932. Valve’s decision to file a suit would indicate that it has ignored the publisher’s warning.

Valve says that it is not pleased with the arbitrator’s $2.39 million declaration, considering it too small, yet it had previously agreed to honour arbitrator’s verdict regardless of outcome. The developer argues that Activision’s allegations of overpayment should have been bought forward to the arbitrator before its verdict, rather than adjusting payments afterwards.